Telephone system



Dec. 4, 1928.

3 Sheelzs-Sheei 1 w. KROLL TELEPHONE SYSTEM Dec. 4, 1928.

3 Sheeis-Sheet 5 Filed July 31, 1926 Patented Dec. 4, 1228.

UNITED )STATEISVPAT-ENZT OFFICE.

WALTER KROLL, F BERLIN, GERMANY, ASSIGNOR TO SIEMEN8 HALSKE ARTER- 'GE SELLSCHAFT, WEBNERWERK, OF SIEMENSSTADT, NEAR BERLIN, GERMANY.

-Applicat0n filed m 31, 1926, SeriaI No.

The inventionrelates to telephone systems i with automatic working, and especially to those, in which hunting switches are usedfor the last stage in the speaking routes of groups routes. This is achieved by providing the last numerical impulse receiver in the setting up of the connection with'testing devices, which enable calls of different value to be set up over the same connecting devices. These testing devices have their circuits so arranged that they only cause a non-numerical switch located beyond the last number impulse receivingdevice to be positioned when over it lines can be reached that can be used for the call to be set up. Hence the non-numerical switch can only be started up when in setting up a high value (trunk) call there is at wleast one outgoing line still free or is engaged by a low value call (local ,call) and the switch is only started up. for making a low value call when there is at least oneoutgoing line still free.

The drawings show byway of example of the invention a telephone system in which local and trunk callsare set up over the same final selectors and line finders to a group of P. B. X. lines,- which-is larger than the num'-' ber of contacts in .a level of the final selector.

The final selectors are provided with two means of access, one of which is reached for local calls over a group selector, while the other is reached, for trunk calls over a special trunk group selector. The invention is of course not limited to this exampleof carrying out the invention. Local as well as trunk calls could be setup in known manner over the same kind of group selectors. i The Figure 1 shows a preselector VW, which is associated with a subscribers line and over which can be reached a number of groupjselectors. for exampletheone designated by I. GW. This group selector has access to 126,252, and in a -maa 'au ui 15,- 1925.

,a final selector LW, which can also be reached public exchange they terminate at contacts of the line finders as well as at preselectors, of these the Figure 2 shows the preselector VWl associated with the line VL.

The method of operating the arrangement shown. in the Fi res 1 and 2 will now be furtherv describe For this purposefwill first be described the setting up of a local call to the line VL shown in'F igure 2 going to the P. B. Whentherecelver is taken down at the subscribers station N, the preselector V W is started up and in known manner it seizes anidle group selector, for ex-v ample I. GW. When the wipers of reach the line going to the grou selector I. GW the winding I of the relay is energized over the test wiper of the preselector and over the off-normal contact 170 of the group selector. At the same time the relays 1A and B are operated over the loop of the calling subscribers line. The relay C locks itself over .the following circuit earth, contact 20, wind: .ing II of relayG, contact 3a,.winding of V2, battery, earth. Furthermore, the relay C at its contacts 40 and 5cprepares the positloni-ng and steering circuit for the succeeding-final selector. "The ositionin'g of the.

group selector I. GW is e ected by the release of the rela'y A in accordance with the first train of impulses transmitted by the subscriber in known manner. After the group selector has been raised. to the desired level, its wipers are rotated'until an idle final selector, for example LW has been found. Thereupon the following test circuit is closed earth, I

windings I and II of Pfcontact 602,-test wiper of I. GW, winding I of C1, wiper II of the side switch in position 1, battery, earth.

The relays P andCl are energized in this y circui The relay P short circuits its winding I of high resistance at it's contact 7 and at its contacts 8 and 9]) it switches through the speaking leads of-the group selector I. GW

over the wipers to the speaking leads of the final selector LW. At the final selector the relay G1 at its contact 1001 closes a locking circuit for its winding II in series with the winding I; V V

If the calling subscriber now transmits the next train of impulses, the relay A falls back in accordance with the number of impulses, and each time it closes its contact 11a. At the same time at each impulse thecontact 3ais opened and the contact 12a is closed. The opening of the contact 3a removes the short circuit of the relay V1, the latter therefore operates and at its contact 13111, it'applies battery to the lower speaking lead. At each impulse the closing of the contact (13 short circuits the winding of the relay V1, which therefore acts as a slow acting relay and it remains in the operated position for the whole train of impulses. For the duration of the train of impulses the relay B1 is energized over the-lower speaking lead in the following circuit: battery, contacts 13121, 5c, 9;), wiper of LGW, arm III of the side switch in positionl, winding of relay B1, earth. The relay B1 opens its contact l ibl and so revents the side switch moving on after the rst lifting step, whereupon the off-normal contact 18 K is closed. Each time an impulse is received\at the group selector the contact 11a is closed and overit the following circuit is established earth, contacts 40, 11a, 8;, wiper of LGW,

arm IV of theside switch in position 1, winding I of relay A1, contact 15w, resistance V2, battery, earth. The relay A1 at its contact 16a1 closes a circuit for the lifting magnet HM over the arm V of the side switch in position 1. The lifting magnet HM raises the yvipers of the final selector into the desired evel.

At the end of the lifting movement the relay Vl at the group selector LGW falls back,

- because it remains short circuited for some time over contact 3a. It opens the contact 1301 and so interrupts the circuit of the relay B1. The latter closes its contact 1461, thereby establishing the following circuit for the motor magnet S of the side switc h: earth, contacts 1461, 17 a1, arm I of the side switch in position 1, off-normal contact 1870, winding of magnet S, batter earth. The magnet S causes the arms "of -t e side switch to move on into the position 2. In this position is closed the following circuit for the winding II of relay J earth, contacts 1901, 20y, arm III of the side switch in position 2, windi'n II of relay J, battery, earth. The relay closes its contact 217' efore it can open its contact 207'. Therefore the winding III of the relay J is energized over the following route: bate tery, winding III of J, contact21j, side switch arm II in position 2, contact 1901, earth. The

. windings II and III of relay J oppose each energized. Hence the relay J falls back at. once and cannot be again energized, because the side switch has in the meantime been moved into position 3 owing to the magnet S having energized over the arm I in position 2.

On leaving the position 2, the arm III opens the circuit of winding II of relay J. In position 3 the motor magnet S is energized over the back contact 22 and the side switch arm I,

hence the arms reach the position 4. In this position, the same circuit is closed for the motor magnet S of the side switch over the arm I, so that it reaches the position 5. The following circuit for the relay A1 is now established: battery, resistance W2, contact 15w, winding of relay A1, side switch arm III in position 5, contacts 2401, 25k and 26p1,

earth. The relay A1 is operated andcloses V over its contact 1601 and the arm V of the side switch in position 5a circuit for the rotary magnet DM, and energizes over the con-' tact 27 al the winding II of the slow acting relay U. The relay U is operated and by opening-its contact 28a, it prevents the side switch moving out of the position 5. The rotary magnet DM is energized over the above described circuit, and it brings the wipers of the final selector LW into contact with the first bank contacts of theselec'ted level, and at contact 29dm it short-circuits the relay The latter releases and at its contact 16a1 it opens the circuit of the rotary magnet DM. This at contact 29(Zm removes the short circuit from the winding of the relay A1, which is thereforea'gain operated and again ener- 1 gizes the rotary magnet DM over the contact 16a1. The inter-action, of the relay A1 and the rotary'ma'gnet DM causes the wipers to move step by step from one bank contact to the next until an idle line has been found going to an idle line finder. I

If all the lines going in the same direction accessible over the line finder be engaged, the contact 7 Oga is closed as will be described below. Thereby when the relay A1 isoperated 11 test relay P has not been operated. In this 0 I position a busy signal is applied over the arm III-to the windings II of A1 and B1, and the signal is induced in the-windings Iof these relays and thence to the calling subscriber.

'Assuming, however, that the line finder NW shown in Fig. 2 is the first idle switch connected to the level of the final selector LW, the following test circuit is now established; earth, contacts 1901, 30mlc (closed upon the first rotary step of the switch), side switch The magnet S- 115 movement of the, final selector the relay U was maintained energized owing to the intermittent energization of relay A1; the'inte'r- 'ruption of the circiut over its windin II at contact 27411 causes the relay U to fall back and at its back contact 2810 it closes the following circuitfor the motor magnet S 9f the side switch: earth, contacts 14b1,.17a1, 28a, side switch arm I in position 5, winding of the magnet S, battery, earth. The side switch reaches its position 6 and is then moved into position 7 owing to the energization of magnet S over the contact 36p1-and the arm I.

In this position the'circuit of the motor magnet S of the side switch is closed over the contact 80121 and the arm I, hence the side switch reaches the position 8.

However, before dealing further with the circuit changes atthe final selector LW, a description will first be given of the operations affected at the line finder NW (Fig. 2) owing to the energizing of the rela R over the above described testing circuit. henit operates, the'relay R at the line switch NW closes the contact 371", therebyenergizing the rotary.

magnet as follows: earth, interrupter- Uni, back contact 38t1, contact 37, windlng of the rotary magnet D, battery, earth. At'contact 39r the relay R prepares the test circuit.

of the line finder.. The rotary magnet D causes the wipers of NW-to move on until an idle line has been found-going to the wanted P. B. X. If the line VL shown in the I Fig. 2 be idle, the following test circuit for the line finder NW is established: earth,

winding I of relay T1, contact 391', test wiper of ,NW, test lead of thepreselector VWl, which is inits normal position and is associated with'the line VL,-'windings I and II of the relay. T2, battery, earth. Over this T circuit are operated the relay T1 at NW and relay T2 at VWl. The relay T1 at its contact 33H opens the'c ircuit of relay R and at contact 38t1 it opens the circuitof the rotary magnet 'D. Hence the line findercomesto nest on the bank contacts of the line .VL.

The relay T1 also switches through-at its con-'- tacts 40t1 and 41t1 the the wipers of the.line V1,], and it closes'its contacts 42t1 and 43131.

speaking leads over Thereby the test lead coming from the final selector LW'is' at the contact connected over the test arm of NW. to the groups. The relay finder NW to the line 42:1 directly windings of the relay T2 at the preselector VWl, and at the contact 43t1 the winding II of relay T1 is connected in parallel with relay T2 to the test lead. The circuit for energizing the rela T1 (winding I) is opened at contact 391'. it the preselector VWl the relay T2 short circuits its high resistance winding I at its contact 44162. It should be here mentioned that when the preselector VWl is in its normal position, the relay X is continuously ener 'zed over the test wiper. When the line is taken into use over a'line finder, the relay X is bridged by the low resistance winding of the test relay (Pl) at the final selector, hence it falls back. The rela closes its contact 45w located in series wit similar contacts at the presele tacts being associated with e change lines connected to the same line finder and being 105 ated in the circuit of the relay Y. 1

Therelay Y serves to disconnect theline finder NW when all the exchange lines accessible over it are engaged. In that case at contact 46; is closed a circuit for the. relay. G over the back contact 479a. At its contact 489 the relay Gdirectly earths the test contact of the line finder in the bank of the final selector LW, so that its test relay P1 caimot be operated when the test wiper. reaches this contact, When the lines of alI the line finders f, these con NW accessible over the final selector LW are engaged, therelay GA is energized over the contact 49g and similar contacts-0f the cut off relays Y belongin to other P. B. X. line A ,at its contact 479a opens the circuit of-relay G and it closes the contact 509a. The relay G opens the contact 48g and closes the contact 34g, hence the test circuit for the final selector LW is again prepared and the line finder 'NW can be again reached. When the line finder NW is taken into use in. the manner above described, the relay R is energized and it now however closes the following circuit for the-winding I of relay T1: battery, contact 509a, resistance Wlj, contacts, 511' and 391', winding I of relay T1, earth. But this circuit is established only when the test wiper of NW- stands on a contact that is not directly earthed. The. object of, this arrangement will be ex lained when describing the's'etting up of trun calls.

During the position of the line finder, the side switch of the final selector hasreached position Sin the manner described above. In

this position the motor magnet S is energized .in'the following circuit: earth, contacts 14b1 and 80p1, side switch arm I in position 8,

winding of .S,-battery, earth. Hence the side switch reaches the position 9, in which-the magnet S is again energized over the contacts 19c1-and 207' and over the arin I; the .side switch therefore moves into In this o'sition the'ringing current is transmitted .om: the source RQover the arm III to the upper speaking'lead and thence over the position 10.

, the upper wiper and contact 40t1 to the exchange line VL and a calling signal at the P. B. X. and overthe contact 41t1 to the lower speakin lead, which is earthed over the side switc arm II of the final selector In position 10 of the side switch the motor magnet S is energized over a slow interru 'ter LU and over the arm I, so that the. slde switch goes into the position 11. When the contact 521' is closed, the source of ringing current RQ is connected over the arm III and a winding I of relay U .to the it is not operated by ringing current over its speaking lead of this exchange line, middle,

winding I. During the ringing pauses the contact 531 is closed, hence battery is directly applied over the winding I ofrelay Uv to the upper speakin lead. \Vhen the P. B. X. answers the cal, the line loop of the exchange line VLis closed and the relay U is operated ,by its winding I. The relay closes its contact 54'u,.hence the motor magnet S of the side switch is energized in the following circuit: earth, contacts 14b1,17a1,' 54a, arm I of the side switch in position 11, winding of ma et S, battery, earth. The side switch reac es its position 12, in which the relays A1 and B1 are energized in the following circuit: earth, battery, resistance W2, contact 15112, winding of relay A1, side switch arm III,-wiper of LWficontact t1,

arm of NW ulger lead of the line VL, which at the P. is connected to the lower Ki er of NW, contact 41t1, middle wiper of B1, earth. "The establishment o the connection at the P. B..X. can'be effected in any "desired'manner. v

At the end of the conversation when-the N has also hung up his receiver the relays A-andB have fallen back at the roup selector LGW. At its contact 120. t e relay A short circuits the windin I I of-the relay 0,

"which falls back after a ittle while and at its contact-.20 opens the circuit of the relay net S over the f0 l V2.. The latter: atcontact 6'v2opejns the holding circuit overtthewmdings I-and II of relay P. The relay P at its contacts 8;)

and 9 opens the speakin selector, ,while the relays 5501, thereby energizing the side'swltch mag-L lowing route earth, con-' leads at the group side switch arm II, windin of relay 1 closes it'scontact 'tacts'56 b1, 5', 5501, side switch arm I in the position 13, winding of magnet S, battei'y, earth. The side switch reaches the po sit-ion 14, in which. the magnet S is energized in the same manner as in. position 12 over arm I, and the side switch ismoved into the position 15. The following circuit for the release magnet M of the final selector LW is now closed: earth, contact 5801, arm I of the side switch, winding of the release magnet M,-battcry, earth. The magnet M in known manner returns the final selector to its normal position, in which the oil -normal contact597c is' closed, hence the magnet Sof the side switch is energized in parallel with the winding of the magnet M.

The side switch reaches the position 16,-1n which the magnet S operates in the same circuit and the side switch is moved into its normal position. g

Upon the release of the connection at the P. B. X. the release of the relay A1- at the final selector also opened the'contact 60a1, hence the engaged condition is removed from the line finder andythe lineVL. The relays H, T1, T2 fall back and the relay X isagain energized over the windings I and II of T2. At the line finder'NW the rela contact 3 8t1, thereby closing t e interrupter circuit for the rotary magnet-of this switch over the arm d. The wipers of the line finder N W are now moved on until the arm d leaves its segment, whereupon the circuit of the rotary magnet D is o ened and the switch has" reached its norma T2 removes the engage preselector VWl by closing the contacts 61252 and 62t2, while therelay X opens its contact 55m in the circuit of the relay Y.

The setting up of an incoming trunk 'call to a P. 'B. X. line will now be described. In 1 is shown a cord circuit and a multi 1e jac VKZ forming part of the. connecting evices at the positionFPl of a trunk operator.

In order to set up a toll call, the operator inserts the plug St of an idle cord circuit into an idle ack such as VKZ. This starts up the.

trunk preselector FV W, 1 indicated in Fig. 1 and it' takes into use an idle'group selector "EGWV; Having operated a key IVS, the opover the test lead,and at contact 1001 closes a locking circuit for its windings I and II.

.When the trunk operator transmits the next train of impulses, the relayAlis'energized by each impulse over the plug St, jack VKZ, up-

per speaking lead'at the-trunk preselector T1 closes its dposition. The relay condition from the Ill and trunk "group selector and over the side switch arm IV,in the position 1. Thggplay the following route: earth, winding magnet HM over the contact 16a 1 and the magnet sets the final selector onto the desired level. At the end of the train of impulses the contact at at the trunk position FPZ is opened, thereby at the final selector releasing the relay B 1, which was energized over the contact a and. the lower speaking lead during the train of impulses. Over-the contacts 1461, 17a1 and 1870 is established a circuit for "the side switch magnet S. The side switch goes into position 2. Now for trunk calls an additional impulse is transmitted after the end of the impulse trans mission. This is effected by closmgthe con tact 82 at the trunk osition; winding I of the relay J is there y energized over the arm IV of the side SWlllChlH position 2. At the same time over the contact 1901 and the back contact 20 is established a circuit for the winding 'II of the relay J, which closes a circuit for its winding III over its contact 21 and the side switch arm II in positions 2.

to 4. The relay J having been energized in position 2 of the side switch by its winding I, it remains energized in position 3 over its contact 21y' and the side switch arm II. The

side switch is at once moved from position 2 into position 3, because its magnet S is energized over the arm I. But the contact 227' is now open, hence for the present side switch remains in this position. For the purpose of initiating the test, the trunk operator presses plied to the lower speaking ead an the relay B1 at the final selector LW is energized over the arm III of the side switch. At its contact 6361, the-relay B1 locks itselffoygelr 0 i side switch arm IV, contacts 63b1, 64a and 65;)1, winding of-relay V3, contact 1510, re-

sistance W2, battery, earth. The relay V3 is also energized in this circuit, hence the 'following circuit is established for the magnet S of the side switch: earth, contacts 66b1, 67'v3, 68 03, arm Iin position 3, winding of magnet S, battery, earth. The side switch reaches the position 4, in which the rotary magnet DM is operated in parallel with'the side switch magnet S in the circuit that hasjust been described. At the same time the relay V3 has closed its contact 6903, thereby connecting the winding I of rela H to the test wiper of the final selector L The rotary magnet now brings the wip- 4 ersof the final selector LW onto the first contact of the selector level. The test wiper ofthe final selector reaches a preliminary test contact, which is connected to'battery over the contact 7 Oga when all the line-finders-connected to the selected levelare engaged. In

that case the relgy QA is energized in the manner already I of relay H, which is connected to the test escribed. The winding I wiper, is then energized. The relay H is o'per- .ated, and at its contact 71bit closes a locking circuit for its windingII, which extends over contact 1901 to earth, In the meantime the side switch has reached the position 5.

At its contact 71dm therotary magnet DM shunts the winding of relay V3 by a low resistance W3, hence the relay falls back after a little while, and interrupts the circuit of the rotary magnet DM at contact. 672:3. Furthermore, in position 5 the short circuit is removed from rela-y .T at the arm II, hence the relay is operated in series with the winding III of relay J over the contact 727'and I the multiple contact 30mk if the test wiper of the final selector LW reaches an idle or a locally engaged 'line finder. If the line' finder be engaged by a trunk call, earth is thewinding of relay T is short circuited over the test wiper, the contacts 32%, 3111.1,

7 3h, side switch arm II in position 5, contact 21d, and it cantherefore not operate. At its contact 71m, the rotary magnet DM now opens the short circuit of the. winding of relay V3, whichtherefore operatesand again closes the circuit of the rotary magnet'DM at contact 67113. The interaction between the relay V3 and the rotary .magnet' DM con- 'tmues until a locally engaged line finder has 'been' found." Thereupon the relay T is operated, because its winding is no longer short circulted, and'at contact 64t'it opens the circuit of the relays V3 and. B1. These relays fall back and the relay V3 at its contact 67 03 opens'the circuit of the rotary magnet DM, while the relay B1 at its contact 1461 closes a circuit for the motor magnet S of the side switch, which extends over the con-' taets 17:11 and 281.1. and over the arm I of the side switch. In position 6 of the side switch, the magnet S is energized over the contacts 56b1, 741 and overthe arm- I, and

operator. The latter can then communicate speaking lead and energizing the relay G1 over the contacts 77 t and 78111. -At its contact 7991 the relay GI closes the following.

circuit for the magnet S of the side switch: earth, contacts 5661, 7415,7991, arm IV in-position 7, winding oif magnet S, battery, earth. k

The side switch goes into position 8, in-which earth is applied to both speaking leads over the arms. III and IV and over the contacts 7 5t and 7 6t, thus in known manner releasing theexisting local connection. The, relayPl can then operate overIthe test wiper of the lac final selector LW and over the side switch arm V,.and closes its contact 80p1. Thereby the-magnet S is energized over the contact 1461 and the arm I of the side switch, hence the side switch goes into the position 9, in which it remains until the end" of the" trunk conversation. Over the contact 8111 and over the arm II the P1 is short circuited and earth apply ringing current to the exchange line taken into use over the following'circuitz battery, source of ringing current RQ, contacts 8691 and 84g, side switch arm III, con- .tact 7 5t, upper speaking lead LW, contact 40t1, at NW, upper speaking lead of the line VL, ringer at the 'P. B. X., lower speaking lead of the exchange line VL, contact 41t1,

lower speaking lead of LW, contact 7 6t, side switch arm IV, contact 85g, earth. To stop the ringing current the operator returns the key PT to its normal position, the relay Q therefore falls back, at its contacts 84g and 85g it disconnects the rin 'ng current and at its back contacts 874 an 88g it establishes the speaking circuit. When the P. B. X. an-

swers the call, the relays A12 andBl are energ ized, but this has no effect for a trunk call.

he release of the trunk connection is controlled by the supervising trunk operator.

The withdrawal 0 the plug St from the jiack VKZ in known manner causes the release of the trunk lector LW, hence the relay G1 falls back. The latter at contact 1901 opens the locking circuit of the relays J and T. Therelay '1 at its contact 57t closes the following circuit .for the release magnet M of the final selector .LWz' earth, contacts 56b1,*57t,' 5501, arm

V in position 9, winding of the release ,inagnet M, battery, earth. I he release magnet in known-manner causes the final selector LW to return to its normal position, in which the.

c-f-normal contact 59k is closed, and the mag:

nets of the side switch is thus energized in parallel with the release magnet M. ,The side switch reaches theposition 10, and the energizing of magnet S over. the slow .in'- terrupter LU and thearm- I causes itto g0 into position 11. In this osition the magnet'S is energized over t e contacts 56b1, 57t, 5501' and over arm I and it brings the side switch into position 12. In this position the circuit of the magnet S extends over the contacts 14b1, 17a1 and over the arm I, hence theside switch goes into position 13. It is reoup selector FGW, which inter rupts the locking circuit for the final se-' turnedto its normal position through the positions 14, 15, 16 in the manner described above. When the trunk operator initiates the test, if there be free outgoing lines from the line- I finders of the selected'level, the relay H can not be operated after the contact 69123 has been closed, because the contact 7 Oga is open, and the relay T remains short circuited in the positions 4 and 5 of the side switch. In the' position 5 of the side switch the short circuit extends over' the contact 217', arm II and over the back contact 89h. The alternate action of the relay V3 and the rotary magnet DM continues until the relay Pis operated by the test arm of LW reaching an idle outgoing line. Thereupon itopens the contact (35101, whereby the circuit for the relays B1 and V8 is opened. The remainder of the circuit changes are similar to those described above for the setting up of a local call.

When a call is originated from the P. B.- X. over the line VL, the windings I and II of relay R1 are energized at the preselector over the contacts 61152 and 6222. At contact-907"" the following circuit is closed for the rotary magnet D1: earth, interrupter Un2, contacts 91t2,90r, winding of D1, battery, earth. The

preselector V W1 is started up and in known manner it takes into use an idle group selector of the public exchange. When the test wiper of V W 1 leaves its normal position,

the test lead connected to the line finder NW is interrupted, the exchange line 'VL therefore cannot be taken into useby the line finder NW. At the same time, the relay X falls back and its contact 450: closes at point in the circuit of the cut-off relay-Y. When the wipers reach'an idle group selector, the

relay T2 is energized over its windings I and- 1 II, and. at its'contact 91t2 it opens the interrupter circuit of the rotary magnet D1, at contact 44252 it short circuits its high resistance winding I and at the contacts 92t2 and 93t2 it switches through the incoming line to the speaking leads going to the group Sc lector. The remainder of the setting u of a I call over the switches in the public exc an' takes Iace in known manner, soit need not descri ed here.

What isclaimed is: 1. In a telephone system, a combination toll and local rotary connector for use by an 0 I erator orlocal subscribers, a group of pro vate branch exchange lines, non-numerical switches having access to said lines, means for operating said connector to select one of said,

non-numerical switches, and means responsive to said selection for operating said nonnumerical switch to connect with one of said lines.

2. A telephone system as characterized by I claim 1 in which, means is provided for preventing the seizure of a non-numerical switch unless at the time it is tested oneor more of the lines to which it has access are available for handling the call.

' 3. A telephone system as characterized by claim 1 in which means is providedfor preyenting the seizure of a non-numerical switch means of said connector non-operable for extending a local call.

5. A telephone system as characterized by claim 1 which includes a test relay in said non-numerical switch which is independent of the testing devices in said connector.

6. A telephone system as characterized by claim 1 which includes atest relay in said nonnumerical switch which is independent of the testin devices in said connector, and means contro led by said test relay for directly connecting the test wiper of said connector to the test lead of said connected line.

7. In a telephone system, a group'of branch exchange lines divided into subgroups, a plurality of non-numerical switches each having access to a different subgroup, a combination toll and local .rotary connector for use by an; operator or local subscribers having access to said non-numerical switches, means for operating said connector to select one of said non-numerical switches, means responsive to said selection for operating said non-numerical switch to connect with one of said lines, means operated when all the lines in one of said subgroups are-busy for rendering the associated non-numerical switch non-selectable from said connector, and means operated when all the lines in all the subgroups are busy for again rendering said non-numerical switch selectable if said connector has been taken into use by an operator.

8. In a telephone system, a combination toll and local connector, a second switch accessible to said connector, a line, means for operating said second switch to connect with said line,

and means for operating said connector when used as a local connector to seize said second switch providing it is not connected to said line, and for operating said connector when used as a toll connector to seize said second switch under certain conditions irrespective of whether or not. said switch is connected to 60 said line.

In witness whereof, I hereunto subscribe my name this 5th day of July, AsD. 1926.

v WALTER KROLL. 

